The invention relates generally to wind turbines, and more specifically to a lightning protection system and method for wind turbines and their associated blades.
A wide variety of lightning protection systems for protection of wind turbines and their associated blades are known within the art. Wind turbines are usually erected in open spaces or in more recent years at sea where they form the highest point and often attract lightning. The tips of the wind turbine blades reach the highest position and are therefore the usual place of impact for lightning.
In the past, the fact that blades were often made of a non-conductive material such as glass fibre lead to the belief that lightning was not a problem. However, such blades are often covered by a thin layer of dust, salt or pollution and together with moisture, the risk of conducting a current is real and results in several unprotected blades being damaged or destroyed by lightning.
The issue of establishing lightning protection for wind turbine blades has generated several different solutions. One solution is intended to prevent the electrical current from a lightning striking the blades of the wind turbine from entering the generator and other electrical and electronic components situated in the top of the wind turbine. This is done by conducting the electrical current from the blades to the tower of the wind turbine and to the ground.
Based on their height and exposed positions, wind turbines offer preferred impact positions for lightning strikes. Wind turbine installations in regions with high ceraunic activities especially require sophisticated protection systems. Most endangered components are the electrical installations, the control electronics and the blades. Later ones are manufactured of glass-fiber reinforced plastics. Their damage or destruction due to lightning results in the longest down-time of the facility.
Modern wind turbines are equipped with blades of approximately 50 m length. Although being made of electrically insulating glass-fiber reinforced plastics, the blades form preferred impact spots for a lightning discharge. To avoid damage or destruction by lightning strikes, these blades are equipped with a lightning protection system (LPS). The most common LPS consists of several metallic discrete receptors that are implemented into the blade shell and that are internally connected to ground by a down-conductor. The receptors provide defined impact positions for the lightning strike. For shorter blades, this concept proved to be sufficient, but for longer blades, some portions of the blade surface continue to be unprotected.
Due to this problem, alternative lightning protection systems have been proposed. One system includes the lamination of a metallic lattice, conductive and flexible foils onto the outer blade shell. The processing step of including metallic lattice into the lamination procedure however, makes later ones more complicated and can also increase the costs due to the higher material expenses.
In view of the foregoing, it would be advantageous to provide a turbine blade lightning protection system that avoids these problems and expenses.